Magnetic recording medium, and method for producing and inspecting the same

ABSTRACT

The present invention provides a method for inspecting deposition characteristics of a deposit on the surface of a protective film predominantly containing carbon of a magnetic recording medium, which medium includes a disk and the protective film formed on the disk, the disk including a non-magnetic substrate, a non-magnetic undercoat layer, and a magnetic layer, the layers being formed on the substrate, wherein the method includes comparing a predetermined threshold with the extraction amount of an inspection gas component and/or a compound component formed so as to contain the inspection gas component, the gas component and/or the compound component being extracted with an inspection solvent after the magnetic recording medium is allowed to stand in an atmosphere of the inspection gas component; a process for producing a magnetic recording medium in which the extraction amount is equal to or greater than the threshold, the extraction amount being obtained through the inspection method; and a magnetic recording medium produced through the production process.

[0001] This application claims benefit of earlier applications based onPatent Application No. 2000-231114 filed in Japan (Filed: Jul. 31,2000),and Provisional U.S. Patent Application No. 60/246595 (Filed: Nov. 8,2000).

TECHNICAL FIELD

[0002] The present invention relates to a magnetic recording medium, aproduction process for the medium, and an inspection method for themedium; and more particularly to a magnetic recording medium exhibitingexcellent durability, a production process for the medium, and aninspection method for the medium.

BACKGROUND ART

[0003] A hard disk apparatus, which is a type of magnetic recording andreproducing apparatus, includes a magnetic recording medium, and amagnetic head for recording data onto the medium and reproducing thedata therefrom. Recently, recording density of the hard disk apparatushas been increased by 60% per year, and this trend is expected tocontinue in the future. Therefore, a magnetic recording head and amagnetic recording medium which are suitable for realization of highrecording density have been developed.

[0004] A magnetic recording medium employed in a magnetic recording andreproducing apparatus or the like basically includes the structure asdescribed below. On a substrate containing an Al alloy coated with Ni—Pthrough plating or on a glass substrate, a non-magnetic undercoat layerfor determining crystal orientation of a Co alloy layer is formed fromCr or a Cr alloy such as CrW or CrMo through sputtering among othermethods. A thin film of Co alloy, serving as a magnetic layer, is formedon the non-magnetic undercoat layer. In addition, a protective filmformed of an element such as carbon is provided on the magnetic layer,and if necessary, a lubricant such as perfluoropolyether is applied ontothe protective film.

[0005] In recent years, requirement for high recording density of amagnetic recording medium has been increasing, and there has been demandfor a magnetic recording medium which enables reduction in spacing loss(i.e., distance between a magnetic recording head and a magnetic layer).In order to reduce spacing loss, studies have been performed on thinningof a carbon protective film and reduction in the flying height of amagnetic recording head. In order to form a carbon protective film,sputtering or plasma CVD has been carried out.

[0006] A criterion for evaluating durability of a magnetic recordingmedium is fly stiction characteristic. The term “fly stictioncharacteristic” refers to a characteristic represented by a stictionvalue of a magnetic recording medium, which value is obtained when themedium is subjected to CSS (contact-start-stop) operation after therotation of the medium and the flight of a magnetic head are maintainedfor a predetermined time. When the fly stiction characteristic of amagnetic recording medium is lowered, the flight stability of a magnetichead is lowered, which may result in problems such as head crushattributed to contact between a protective film and the magnetic head.Particularly, a medium of high recording density is used while theflying height of a magnetic head is maintained at a low level, and thussuch a medium is demanded to exhibit excellent fly stictioncharacteristic.

[0007] However, a magnetic recording medium produced through theaforementioned conventional art may exhibit poor fly stictioncharacteristic. One of the reasons is thought to be as follows: whendeposits are deposited onto the surface of such a magnetic recordingmedium in a magnetic recording and reproducing apparatus, and when themedium is employed for a prolonged period of time, the deposits aredeposited onto a magnetic head, and thus fly stiction characteristic ofthe medium is lowered. One of such deposits is thought be a compoundcontaining a gas component generated in the magnetic recording andreproducing apparatus or a compound which is formed through reactionbetween the gas component and an ionic substance contained in theapparatus, such as a metal. For example, a variety of members employedin the magnetic recording and reproducing apparatus are produced fromplastic materials such as resin or photo-curing resins. A plasticizersuch as a phthalate or a compound such as a photoreaction initiator isgenerated as an impurity gas component from such a material. Moreover, alubricant employed in a pin of a connector part is present as animpurity gas component in the magnetic recording and reproducingapparatus. In order to maintain cleanliness of the magnetic recordingand reproducing apparatus, the inside of the apparatus is segregatedfrom the outside. Therefore, such a gas component generated inside theapparatus remains therein in a certain form, and a portion of thecomponent is thought to become a deposit. When a magnetic head has thedeposit on its surface, writing of data onto a magnetic recording mediumor reading of the data therefrom may be unsatisfactory in practical use.

[0008] Therefore, there has been demand for a magnetic recording mediumon which deposits are not easily deposited, the medium being employed ina magnetic recording and reproducing apparatus of high recordingdensity. However, at the present time, there is no available method forinspecting the degree of difficulty in deposition of deposits onto amagnetic recording medium.

DISCLOSURE OF INVENTION

[0009] In view of the foregoing, an object of the present invention isto provide a method for inspecting the degree of difficulty indeposition of deposits onto a magnetic recording medium; a magneticrecording medium on which deposits are not easily deposited; a processfor producing the medium; and a magnetic recording and reproducingapparatus comprising the medium.

[0010] The present inventors have performed extensive studies, and havefound characteristics of a gas generated in a magnetic recording andreproducing apparatus, characteristics of a deposit on a carbonprotective film of a magnetic recording medium, and characteristics ofthe carbon protective film. The present invention has been accomplishedon the basis of this finding.

[0011] 1) A first invention for solving the aforementioned problemsprovides a method for inspecting deposition characteristics of a depositon the surface of a protective film predominantly containing carbon of amagnetic recording medium, which medium comprises a disk and theprotective film formed on the disk, the disk comprising a non-magneticsubstrate, a non-magnetic undercoat layer, and a magnetic layer, thelayers being formed on the substrate, characterized in that the methodcomprises determining that the extraction amount of an inspection gascomponent and/or a compound component formed so as to contain theinspection gas component is equal to or greater than a predeterminedthreshold, the gas component and/or the compound component beingextracted with an inspection solvent after the magnetic recording mediumis allowed to stand in an atmosphere of the inspection gas component.

[0012] 2) A second invention for solving the aforementioned problems isdrawn to a specific embodiment of the inspection method according to 1),wherein the inspection gas component is a gas generated in a magneticrecording and reproducing apparatus comprising a magnetic recordingmedium and a magnetic head for recording data onto the medium andreproducing the data therefrom.

[0013] 3) A third invention for solving the aforementioned problems isdrawn to a specific embodiment of the inspection method according to 1)or 2), wherein the inspection gas component is one or more selected fromamong a siloxane-containing gas, an acrylic-acid-containing gas,vaporized melamine, a vaporized lubricant, a vaporized higher fattyacid, a vaporized phthalic acid ester, and vaporized dioctyl phthalate.

[0014] 4) A fourth invention for solving the aforementioned problems isdrawn to a specific embodiment of the inspection method according anyone of 1) through 3), wherein the inspection gas component is a gascomponent generated from a member employed inside the magnetic recordingand reproducing apparatus.

[0015] 5) A fifth invention for solving the aforementioned problems isdrawn to a specific embodiment of the inspection method according anyone of 1) through 4), wherein the inspection solvent is one or moreselected from among methanol, ethanol, isopropyl alcohol, and water.

[0016] 6) A sixth invention for solving the aforementioned problems isdrawn to a specific embodiment of the inspection method according anyone of 1) through 5), wherein the threshold is 0.06 [μg/100 cm²] whenthe extracted component is melamine.

[0017] 7) A seventh invention for solving the aforementioned problemsprovides a magnetic recording medium comprising a non-magneticsubstrate; a non-magnetic undercoat layer and a magnetic layer, thelayers being formed on the substrate; and a protective filmpredominantly containing carbon, the film being formed on the magneticlayer, characterized in that the extraction amount of an inspection gascomponent and/or a compound component formed so as to contain theinspection gas component is equal to or greater than a predeterminedthreshold, the gas component and/or the compound component beingextracted with an inspection solvent after the magnetic recording mediumis allowed to stand in an atmosphere of the inspection gas component.

[0018] 8) A eighth invention for solving the aforementioned problems isdrawn to a specific embodiment of the magnetic recording mediumaccording to 7), wherein the threshold is 0.06 [μg/100 cm²] when theextracted component is melamine.

[0019] 9) A ninth invention for solving the aforementioned problems isdrawn to a specific embodiment of the magnetic recording mediumaccording to 7) or 8), wherein a peak of the infrared spectrum of thesurface of the protective film predominantly containing carbon, the peakcorresponding to a carbon-hydrogen bond, has an intensity of 0.055 orless.

[0020] 10) A tenth invention for solving the aforementioned problems isdrawn to a specific embodiment of the magnetic recording mediumaccording to any one of 7) through 9), wherein the ratio of nitrogen tocarbon in the protective film predominantly containing carbon is 5-40 at%.

[0021] 11) A eleventh invention for solving the aforementioned problemsis drawn to a specific embodiment of the magnetic recording mediumaccording to any one of 7) through 10), wherein Id/Ig of the surface ofthe protective film predominantly containing carbon is 3.5 or less.

[0022] 12) A twelfth invention for solving the aforementioned problemsprovides a process for producing a magnetic recording medium, whichprocess comprises forming a protective film predominantly containingcarbon on a disk comprising a non-magnetic substrate, a non-magneticundercoat layer, and a magnetic layer, the layers being formed on thesubstrate, characterized in that the protective film is formed such thatthe extraction amount of an inspection gas component and/or a compoundcomponent formed so as to contain the inspection gas component is equalto or greater than a predetermined threshold, the gas component and/orthe compound component being extracted with an inspection solvent afterthe magnetic recording medium is allowed to stand in an atmosphere ofthe inspection gas component.

[0023] 13) A thirteenth invention for solving the aforementionedproblems is drawn to a specific embodiment of the production process fora magnetic recording medium according to 12), wherein a formationprocess for the protective film predominantly containing carboncomprises a sputtering process in which the protective film is formedwhile bias is applied to the disk.

[0024] 14) A fourteenth invention for solving the aforementionedproblems is drawn to a specific embodiment of the production process fora magnetic recording medium according to 12), wherein a formationprocess for the protective film predominantly containing carboncomprises a plasma CVD process in which a reaction gas containinghydrocarbon is employed as a raw material.

[0025] 15) A fifteenth invention for solving the aforementioned problemsis drawn to a specific embodiment of the production process for amagnetic recording medium according to 12), wherein a formation processfor the protective film predominantly containing carbon comprises aformation step including a plasma CVD process in which a reaction gascontaining hydrocarbon is employed as a raw material, and a formationstep including a sputtering process in which the protective film isformed while bias is applied to the disk.

[0026] 16) A sixteenth invention for solving the aforementioned problemsprovides a magnetic recording and reproducing apparatus comprising amagnetic recording medium and a magnetic head for recording data ontothe medium and reproducing the data therefrom, characterized in that themagnetic recording medium is a magnetic recording medium as recited inany one of 7) through 11).

[0027] As used herein, the term “atomic %” may be abbreviated as “at %.”As used herein, “1 nm” refers to “10 Å.”

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a cross-sectional view of one embodiment of the magneticrecording medium of the present invention.

[0029]FIG. 2 shows the amount of deposits on the surface of a magneticrecording medium versus the total amount of diffusion gas.

[0030]FIG. 3 is a schematic representation showing a magnetic recordingand reproducing apparatus including the magnetic recording medium shownin FIG. 1.

[0031]FIG. 4 is a schematic representation showing a plasma CVDapparatus employed for carrying out one embodiment of the productionprocess for a magnetic recording medium of the present invention.

[0032]FIG. 5 is a schematic representation showing a protective filmmodification apparatus employed for carrying out one embodiment of theproduction process for a magnetic recording medium of the presentinvention.

[0033]FIG. 6 is a schematic representation showing a sputteringapparatus employed for carrying out one embodiment of the productionprocess for a magnetic recording medium of the present invention.

[0034]FIG. 7 illustrates the mean voltage and the positive voltage peakvalue of pulse direct-current bias.

BEST MODES FOR CARRYING OUT THE INVENTION

[0035] One embodiment of the inspection method of the present inventionwill be described.

[0036] The inspection method of the present invention is roughlydescribed below.

[0037] The inspection method of the present invention includes a step inwhich a magnetic recording medium serving as a sample is allowed tostand in an atmosphere of an inspection gas component, to thereby exposethe surface of the medium to the inspection gas component, the mediumincluding a protective film predominantly containing carbon; a step inwhich the resultant magnetic recording medium is immersed in aninspection solvent, to thereby subject the medium to extraction; a stepin which the extraction amount of the inspection gas component and/or acompound formed so as to contain the gas component in the inspectionsolvent is measured after completion of immersion; and a step fordetermining that the extraction amount is equal to or greater than apredetermined threshold.

[0038] Conventionally, a magnetic recording medium including aprotective film having deposits on its surface is immersed in a solvent,and then the extraction amount of the deposits in the solvent ismeasured. When the extraction amount is small or when the amount isequal to or lower than a certain threshold, the magnetic recordingmedium is considered to have a small amount of deposits; i.e., themedium is considered to not be prone to the deposition of deposits onits surface. In contrast, according to the present invention, after themagnetic recording medium is exposed to an inspection gas component, theextraction amount of the inspection gas component and/or a compoundcomponent formed so as to contain the gas component in an inspectionsolvent, which components may be deposits, is large; for example, theextraction amount is equal to or greater than a certain threshold.

[0039] In the present invention, the amount of deposits on the surfaceof a magnetic recording medium can be determined by the extractionamount of the deposits. The mechanism of the determination is assumed tobe as follows. FIG. 2 shows the amount of deposits on the surface of aprotective film of a magnetic recording medium when the amount ofdiffusion gas to which the medium is exposed varies; for example, due tovariation of the exposure time. As shown in FIG. 2, in region ecorresponding to magnetic recording medium E or in region fcorresponding to magnetic recording medium F, even when the amount ofdiffusion gas increases, deposits are not deposited onto any medium. Asis apparent from FIG. 2, the medium F is not prone to the deposition ofdeposits on its surface with respect to the amount of diffusion gas, ascompared with the medium E. The present inventors have considered that,in the region e or f, diffusion gas is not deposited onto the surface ofthe protective film, but is adsorbed in the protective film. The presentinventors have considered that, when the amount of diffusion gas exceedsthe amount of the gas which can be adsorbed in the protective film, theprotective film has deposits on its surface. Therefore, the amount ofdiffusion gas adsorbed in the protective film of the medium F is greaterthan that of diffusion gas adsorbed in the protective film of the mediumE, and thus the protective film of the medium F is not prone to havedeposits on its surface. The extraction amount of deposits as measuredaccording to the present invention can be regarded as the amount of thedeposits adsorbed in the protective film. The magnetic recording mediumof the present invention in which the extraction amount of deposits isequal to or greater than a certain threshold is a magnetic recordingmedium which is not prone to have deposits on its surface, since theamount of the deposits adsorbed in the medium is satisfactorily large.For example, when the extraction amount of deposits on magneticrecording medium A (defective sample), which amount is measuredaccording to the present invention, is regarded as a threshold, theextraction amount corresponding to the magnetic recording medium of thepresent invention is greater than the threshold. Briefly, the amount ofdeposits adsorbed in the medium of the invention is greater than that ofdeposits adsorbed in the medium A. Therefore, the magnetic recordingmedium of the present invention is not prone to have deposits on itssurface.

[0040] A specific inspection procedure will next be described.

[0041]FIG. 1 shows an exemplary magnetic recording medium employed as asample for inspection. The magnetic recording medium includes anon-magnetic substrate S, a non-magnetic undercoat layer 1, a magneticlayer 2, a carbon protective film 3, and a lubrication layer 4, thelayers and film being successively formed on the substrate S.

[0042] Firstly, the sample is allowed to stand in an atmosphere of aninspection gas, to thereby expose the surface of the sample to the gas.For example, the magnetic recording medium is allowed to stand in asealed container capable of introduction and discharge of an inspectiongas, and then the inspection gas is introduced into the container. Whena magnetic recording and reproducing apparatus is employed as such asealed container, the magnetic recording medium can be placed on aspindle in the apparatus, which is preferable. Moreover, when thespindle is rotated in a manner similar to the case of practical use ofthe apparatus, the magnetic recording medium is exposed to theinspection gas in a manner similar to the case of practical use of themedium, which is preferable. The rotation speed may be any value withina range of 4,200-15,000 [rpm].

[0043] The concentration of the inspection gas may be, for example, 3.8[μg/the volume of the inner space of the magnetic recording andreproducing apparatus] (as reduced to siloxane oligomer). Alternatively,the concentration of the inspection gas may be, for example, 15 [ng/cm³](as reduced to siloxane oligomer). In order to accelerate the test, theconcentration of the inspection gas is preferably high.

[0044] The time during which the magnetic recording medium is allowed tostand may be, for example, 24 hours. In order to adsorb the inspectiongas sufficiently into the magnetic recording medium, the time ispreferably sufficiently long.

[0045] The temperature when the magnetic recording medium is allowed tostand in the magnetic recording and reproducing apparatus may be, forexample, ambient temperature. In order to accelerate the test, thetemperature is preferably high.

[0046] The pressure when the magnetic recording medium is allowed tostand may be, for example, ambient pressure. In order to accelerate thetest, the pressure is preferably high.

[0047] When the concentration of the inspection gas is low, the timeduring the magnetic recording medium is allowed to stand or thetemperature when the magnetic recording medium is allowed to stand maybe appropriately regulated (e.g., time: 72 hours, temperature: 40° C.),to thereby adsorb the inspection gas sufficiently into the magneticrecording medium.

[0048] The inspection gas may be a gas generated in the magneticrecording and reproducing apparatus, or may be a component forming acompound which constitutes a deposit on the surface of the magneticrecording medium. When such a gas or component is employed, the case inwhich the magnetic recording medium is practically used in the apparatusand the medium is exposed to the gas can be reproduced, which ispreferable. The inspection gas is preferably one or more selected fromamong a siloxane-containing gas, an acrylic acid-containing gas, astearic-acid-containing gas, vaporized melamine, a vaporized lubricant,a vaporized higher fatty acid (e.g., a fatty acid of C10 or more), avaporized phthalic acid ester, and vaporized dioctyl phthalate. In thecase in which such gas components are employed in combination, when thecombination is similar to the combination of gas components in theapparatus when practically used, the inspection is carried out under theconditions similar to those under which the medium is practically used,which is preferable. Instead of introduction of such a gas, a memberwhich generates gas, such as adhesive tape, resin, or film, may beallowed to stand together with the magnetic recording medium. Forexample, when the magnetic recording and reproducing apparatus isemployed as a container, and a practically used member is allowed tostand therein together with the magnetic recording medium which isplaced on the spindle, the inspection is carried out under theconditions similar to those under which the medium is practically used,which is preferable. When the spindle is rotated, the inspection iscarried out under the conditions more similar to those under which themedium is practically used, which is preferable. In the case in whichsuch a member is employed as a gas generation source, when theconcentration of the gas is unknown, the time during the magneticrecording medium is allowed to stand or the temperature when themagnetic recording medium is allowed to stand may be appropriatelyregulated (e.g., time: 72 hours, temperature: 40° C.), to thereby adsorbthe inspection gas sufficiently into the magnetic recording medium.

[0049] After completion of exposure, the resultant sample is immersed inan inspection solvent as described below, to thereby subject the sampleto extraction. In this case, a target extraction component is theinspection gas component and/or a compound component formed so as tocontain the gas component.

[0050] The inspection solvent may be any solvent, so long as the targetextraction component is dissolved in the solvent. For example, thesolvent is preferably one or more selected from among methanol, ethanol,isopropyl alcohol, and water.

[0051] The amount of the solvent may be, for example, 30 [ml/magneticrecording medium]. In order to enhance extraction efficiency, the amountis preferably large.

[0052] The extraction time may be, for example, one hour. Whenextraction ability of the solvent is low, the sample is preferablyallowed to stand in the solvent for a prolonged period of time.

[0053] The temperature during extraction may be appropriately determinedin accordance with the type of the inspection solvent, and may bedetermined at, for example, 80° C. In order to enhance extractionefficiency, the temperature is preferably high.

[0054] Subsequently, the target extraction component in the inspectionsolvent is quantitatively measured, for example, through a customaryquantitative method by means of GC-MS.

[0055] The threshold is determined, for example, as described below. Thethreshold may be determined on the basis of the extraction amount asmeasured through the aforementioned method in the case in which, as asample, there is employed a magnetic recording medium exhibitingdurability which is required in practical use in a magnetic recordingand reproducing apparatus. Alternatively, the threshold may bedetermined on the basis of the extraction amount as measured through theaforementioned method in the case in which a magnetic recording mediumexhibiting poor durability is employed as a sample. For example, thethreshold may be determined on the basis of the extraction amount asmeasured through the aforementioned method in the case in which amagnetic recording medium exhibiting poor fly stiction characteristic isemployed as a sample or in the case in which a magnetic recording mediumhaving deposits on its surface is employed as a sample, the depositsbeing observed after exposure to an inspection gas. The threshold may beobtained by multiplying the measured extraction amount by a safetyfactor. For example, when the extraction amount corresponding to adefective magnetic recording medium is X, the threshold may bedetermined to be X. Alternatively, by using α as a safety factor, thethreshold may be determined to be (X×α).

[0056] The inspection of a magnetic recording medium serving as a sampleis carried out by comparing the extraction amount of the sample asmeasured through the aforementioned method with the threshold asdetermined through the aforementioned method, and by determining thatthe extraction amount is equal to or greater than the threshold.

[0057] According to a conventional inspection method, when theextraction amount is large or when the amount is equal to or greaterthan the threshold, the magnetic recording medium is determined to bedefective. Therefore, a magnetic recording medium having a large amountof deposits not on its surface but inside thereof may be determined tobe defective. In contrast, according to the inspection method of thepresent invention, a magnetic recording medium having a large amount ofdeposits inside thereof can be appropriately determined, since theextraction amount is equal to or greater than the threshold afterexposure of the medium to an inspection gas. Consequently, the degree ofdifficulty in deposition of deposits onto the magnetic recording mediumcan be appropriately determined.

[0058] One embodiment of the magnetic recording medium of the presentinvention will be described.

[0059]FIG. 1 shows an example of the magnetic recording medium of thepresent invention. The magnetic recording medium includes a non-magneticsubstrate S, a non-magnetic undercoat layer 1, a magnetic layer 2, aprotective film 3 predominantly containing carbon, the layers and thefilm being formed on the substrate S, and a lubrication film 4 formed onthe film 3.

[0060] The non-magnetic substrate S may be an aluminum alloy substrateon which an NiP plating film is formed (hereinafter the substrate may bereferred to as “NiP-plated Al substrate”), which is generally employedas a substrate for magnetic recording media; or a substrate of glass,ceramic, or flexible resin, which substrate may be coated with NiP oranother alloy through plating or sputtering.

[0061] The mean surface roughness (Ra) of the non-magnetic substrate Sis preferably 1-20 Å, more preferably 1-15 Å.

[0062] The non-magnetic undercoat layer 1 may be a conventionally knownnon-magnetic undercoat layer. For example, the layer 1 may be a singleelement film formed from any element selected from Cr, Ti, Ni, Si, Ta,and W. Alternatively, the layer 1 may be a film formed from an alloycontaining any of the above elements as a primary component and otherelements, so long as such “other elements” do not impede thecrystallinity of the layer 1. The non-magnetic undercoat layer 1 isprovided for controlling the crystal orientation of the magnetic layer 2formed from a Co alloy. The layer 1 is particularly preferably formedfrom a material of Cr single element or a material containing Cr and oneor more selected from among Mo, W, V, Ti, Nb, and Si. When theaforementioned material is employed, the composition is preferably CrzY(wherein Y is one or more selected from among Mo, W, V, Ti, Nb, and Si).The Y content (z) is preferably 20 at % or less, more preferably 10 at %or less. When the Y content is 20 at % or less, the orientation of themagnetic layer 2 formed from a Co alloy, the layer 2 being provided onthe non-magnetic undercoat layer 1, is improved, and therefore themagnetic recording medium exhibits excellent coercive force and noisecharacteristics; i.e., the medium is suitable for realization of highrecording density. As used herein, the term “primary component” in analloy refers to the case in which the content of the component is inexcess of 50 at %.

[0063] The crystal grain size of the non-magnetic undercoat layer 1 mayaffect the crystal grain size of the magnetic layer 2 formed from a Coalloy. The crystal grain size of the non-magnetic undercoat layer 1 maybe reduced by adding an element such as B, Zr, or Ta to the material ofthe layer 1; i.e., Cr or a Cr alloy.

[0064] The thickness of the non-magnetic undercoat layer 1 is notparticularly limited, so long as the thickness falls within a range soas to attain a appropriate coercive force. The thickness is preferably100-1,000 Å, more preferably 150-700 Å. The magnetic recording mediumincluding the non-magnetic undercoat layer 1 having a thickness fallingwithin the above range exhibits enhanced coercive force and improvedSNR; i.e., the medium is suitable for realization of high recordingdensity.

[0065] The non-magnetic undercoat layer 1 may be of a single-layerstructure, or of a multi-layer structure. When the layer 1 has amulti-layer structure, the layer 1 may be formed of a plurality oflayers formed from the same composition or different compositions fromamong the aforementioned compositions. For example, the layer 1 may be amulti-layer structure in which a CrMo alloy layer (Mo content: 10 at %or less) is laminated on a Cr layer.

[0066] The magnetic layer 2 formed from a Co alloy may contain any Coalloy composition selected from among Co/Cr, Co/Cr/Ta, Co/Cr/Pt,Co/Cr/Pt/Ta, and the like.

[0067] The coercive force of the magnetic recording medium of thepresent invention is preferably 3,000 [oersteds] or more, preferably3,500 [oersteds] or more.

[0068] The thickness of the magnetic layer 2 formed from a Co alloyfalls within a range of 30-100 [Gμm], which is a parameter ofconventionally used Brd (the product of residual magnetization and filmthickness [Gμm]), and the thickness of the layer 2 may be a thickness soas to attain an appropriate recording and reproducing signal output.

[0069] In order to improve the orientation of the Co alloy and to obtainhigh coercive force, a non-magnetic intermediate layer may be providedbetween the non-magnetic undercoat layer 1 and the magnetic layer 2. Forexample, a CoCr alloy layer (Cr content: 50 at % or less) having athickness of 25 Å or less may be formed.

[0070] The carbon protective film 3 is formed from a materialpredominantly containing carbon. The carbon protective film 3 is formedsuch that the extraction amount of an inspection gas component and/or acompound component formed so as to contain the inspection gas componentis equal to or greater than a certain threshold, the gas componentand/or the compound component being extracted with an inspection solventafter the magnetic recording medium is allowed to stand in an atmosphereof the inspection gas component. The extracted component is preferablymelamine. When the extracted component is melamine, the threshold is0.06 [μg/100 cm²], preferably 0.12 [μg/100 cm²], more preferably 0.24[μg/100 cm²]. Since melamine is a main impurity gas component whichcauses deposition in a magnetic recording and reproducing apparatus, theextraction component is determined to be melamine. The reason why theextraction amount of melamine is determined to the above range isdescribed below. When the extraction amount falls within the aboverange, the amount of impurity gas adsorbed in the carbon protective film3 increases, and thus deposits are not easily deposited onto the carbonprotective film 3 of the magnetic recording medium. The extractionamount can be obtained through the aforementioned method.

[0071] The protective film 3 may contain nitrogen serving as anothercomponent. In this case, the ratio of nitrogen to carbon as measured bymeans of ESCA is preferably 5-40%, more preferably 5-25%, much morepreferably 13-25%. This is because the film containing nitrogen is denseand hard.

[0072] When the carbon protective film 3 contains nitrogen, the filmpreferably contains nitrogen in an amount of 2 at % or less in thevicinity of a surface of the film 3, the surface being brought intocontact with the magnetic layer. This is because, when the amount ofnitrogen falls outside the above range, magnetostatic characteristics ofthe magnetic layer deteriorate and coercive force is lowered, and thusthe magnetic recording medium is not suitable for realization of lowflying height. The amount of nitrogen in the magnetic layer can beobtained by means of, for example, SIMS analysis. As used herein, theterm “the vicinity” may refer to a position on the boundary between themagnetic layer and the protective film, at which the Co content is 5% ofthat of the magnetic layer.

[0073] A dense and hard protective film is preferable, since the filmcan suppress generation of wear powder, which would induce deposition ofdeposits and generation of Ni corrosion. As used herein, the term “Nicorrosion” refers to a phenomenon in which Ni contained in the Ni—Pplating layer on the substrate arises on the surface of the magneticrecording medium through diffusion or the like. Ni corrosion isevaluated, for example, by measuring the amount of Ni after extractionof Ni on the surface of the medium.

[0074] When the carbon protective film 3 is subjected to FTIR, theintensity of the peak corresponding to a carbon-hydrogen bond ispreferably 0.055 or less, more preferably 0.05 or less, much morepreferably 0.04 or less. When the intensity falls within the aboverange, the protective film predominantly containing carbon has a strongbonding force to a lubricant on the film. When the bonding force isstrong, the surface of the protective film is consistently coated withthe lubricant, and thus deposition of deposits can be suppressed.

[0075] Measurement of the intensity of the peak corresponding to acarbon-hydrogen bond by means of FTIR is carried out, for example,through the following procedure. There is prepared an FTIR apparatusexhibiting a sensitivity such that, when a perfluoropolyether-containinglubricant is applied onto a disk so as to have a thickness of 2 nm, themeasured intensity of the peak (e.g., the peak which arises within aregion of 1,120-1,350 cm⁻¹) corresponding to a C—F bond (carbon-fluorinebond) of the infrared spectrum of the disk is 0.008. Firstly, theinfrared spectrum of the protective film predominantly containing carbon(hereinafter the spectrum may be referred to as “the carbon protectivefilm infrared spectrum”) is obtained from the measured-infrared spectrumof the surface of the magnetic recording medium before formation of theprotective film and the measured infrared spectrum of the surface of themagnetic recording medium after formation of the protective film.Subsequently, the area of the peak within a range of 2,800-3,100 cm⁻¹ ofthe infrared spectrum is calculated, and the calculated area is regardedas the intensity of the peak corresponding to a carbon-hydrogen bond. Asused herein, the peak intensity refers to the absorption amount.

[0076] When the protective film 3 is subjected to Raman spectroscopy,the Id/Ig value is preferably 3.5 or less, more preferably 3.0 or less,much more preferably 2.5 or less. This is because, when the Id/Ig valuefalls within the above range, the protective film predominantlycontaining carbon is dense and hard. The Id/Ig value is obtained asfollows: the measured Raman spectrum is separated into two bands; i.e.,a G band having the peak in the vicinity of 1,500 cm⁻¹ and a D bandhaving the peak in the vicinity of 1,400 cm⁻¹; and the ratio of Id (theintegral value of intensity of the D band) to Ig (the integral value ofintensity of the G band) is obtained.

[0077] The water contact angle of the surface of the protective film ispreferably 80° or less, more preferably 75° or less. This is because,when the water contact angle is 80° or less, the protective film issatisfactorily bonded to the lubricant, and thus the lubricant is noteasily deposited onto a magnetic head.

[0078] The thickness of the carbon protective film 3 may be 90 Å orless. The thickness is preferably 75 Å or less, more preferably 50 Å orless. This is because, when the thickness falls within the above range,spacing loss can be further reduced, and thus reproduction signal outputcan be increased.

[0079] The lubrication film 4 is formed through application of alubricant. The lubricant may contain any lubricant selected from among aFomblin-type lubricant (product of Ausimont), a Galden-type lubricant(product of Ausimont), a Demnum-type lubricant (product of DaikinIndustries, Ltd.), and a Krytox-type lubricant (product of Du Pont).

[0080] In order to obtain the aforementioned effect, a Fomblin-typelubricant is preferably employed. This is because such a Fomblin-typelubricant has polar functional groups at both ends of its molecularchain, and the groups are easily adsorbed onto active sites of thecarbon protective film 3.

[0081] The thickness of the lubricant film may be 5-30 Å, and ispreferably 10-25 Å. When the thickness falls within this range, themagnetic recording medium exhibits appropriate lubricity, and thelubricant is not excessively deposited onto a magnetic head, which ispreferable.

[0082] The extraction amount of an inspection gas component and/or acompound component formed so as to contain the inspection gas componentis equal to or greater than a certain threshold, the gas componentand/or the compound component being extracted with an inspection solventafter the magnetic recording medium of the present invention is allowedto stand in an atmosphere of the inspection gas component. Therefore,the protective film predominantly containing carbon of the magneticrecording medium is not prone to have deposits on its surface. When theextracted component is melamine, the threshold is preferably 0.06[μg/100 cm²], more preferably 0.12 [μg/100 cm²], much more preferably0.24 [μg/100 cm²]. Consequently, when the magnetic recording medium ofthe present invention is used while the flying height of a magnetic headis reduced, deposits are not easily deposited onto the head. Therefore,even when the magnetic recording medium is used while the flying heightof a magnetic head is reduced, the fly stiction characteristic of themedium is not lowered. When the carbon protective film 3 is subjected toFTIR, the intensity of the peak corresponding to a carbon-hydrogen bondis preferably 0.055 or less. Therefore, the surface of the protectivefilm is consistently coated with the lubricant, and thus deposition ofdeposits can be suppressed.

[0083] Preferably, the protective film 3 contains nitrogen, and theratio of nitrogen to carbon as measured by means of ESCA is preferably5-40%. Therefore, the film is dense and hard. Preferably, the magneticrecording medium of the present invention includes the protective filmpredominantly containing carbon, which film is hard and thin, exhibitsexcellent sliding durability and lubricity, and suppresses generation ofwear powder inducing deposition of deposits and generation of Nicorrosion.

[0084] By reducing the flying height of a magnetic head and thinning theprotective film predominantly containing carbon, the distance betweenthe head and the magnetic layer serving as a magnetic recording layer isreduced. Therefore, in the magnetic recording medium of the presentinvention, spacing loss can be reduced. Consequently, since reproductionsignal output can be increased and SNR (signal to noise ratio) isimproved, the magnetic recording medium of the present invention is moreapplicable to high recording density, as compared with a conventionalmagnetic recording medium.

[0085] In addition, the coercive force is 3,000 [oersteds] or more,preferably 3,500 [oersteds] or more, and the mean surface roughness (Ra)is preferably 20 Å or less, more preferably 10 Å or less. This isbecause, when the coercive force is 3,000 [oersteds] or more,reproduction signal output can be further increased at high recordingdensity, and when the mean surface roughness (Ra) is preferably 20 Å orless, the flying height of a magnetic head can be further reduced.Consequently, the magnetic recording medium of the present invention ismore applicable to high recording density,.

[0086]FIG. 3 shows an exemplary magnetic recording and reproducingapparatus including the aforementioned magnetic recording medium. Themagnetic recording and reproducing apparatus includes a magneticrecording medium 30 having the structure shown in FIG. 1; a mediumdriving portion 31 for rotating the magnetic recording medium 30; amagnetic head 32 for recording data onto the magnetic recording medium30 and reproducing the data therefrom; a head driving portion 33 formoving the magnetic head 32 relatively to the magnetic recording medium30; and a recorded/reproduced signal-processing system 34. In the system34, a recorded external signal is processed and sent to the magnetichead 32, or a reproduction signal from the head 32 is processed and sentto the outside. A magnetic head including reproduction elements such asan MR (magnetoresistance) element utilizing anisotropicmagnetoresistance (AMR) effect and a GMR element utilizing giantmagnetoresistance (GMR) effect, which head is more suitable forrealization of high recording density, may be employed as the magnetichead 32 of the magnetic recording and reproducing apparatus of thepresent invention.

[0087] The magnetic recording and reproducing apparatus includes themagnetic recording medium of the present invention (the extractionamount of an inspection gas component and/or a compound component formedso as to contain the inspection gas component is equal to or greaterthan a certain threshold, the gas component and/or the compoundcomponent being extracted with an inspection solvent after the magneticrecording medium is allowed to stand in an atmosphere of the inspectiongas component). Since deposits are not easily deposited onto the surfaceof the magnetic recording medium, the magnetic head is not prone tohaving deposits on its surface even when the flying height of the headis reduced. Therefore, the flying height of the magnetic head of theapparatus can be further reduced, and thus the magnetic recording andreproducing apparatus of the present invention is applicable to higherrecording density. The magnetic recording and reproducing apparatusexhibits excellent fly stiction characteristic.

[0088] The production process for the magnetic recording medium of thepresent invention will next be described.

[0089] (Apparatus Employed for the Production Process)

[0090] The CVD apparatus and the protective film modification apparatusemployed in the present invention will be described.

[0091]FIG. 4 shows a schematic representation of a plasma CVD apparatusserving as a main portion of the production apparatus employed forcarrying out an embodiment of the production process for the magneticrecording medium of the present invention. The plasma CVD apparatusincludes a CVD apparatus chamber 10 for accommodating a disk D on whicha protective film predominantly containing carbon is formed; electrodes11, 11 provided on opposing walls in the CVD apparatus chamber 10 so asto face each other; high-frequency power sources 12, 12 for supplyinghigh-frequency power to the electrodes 11, 11; a bias power source 13which may be connected to the disk D in the CVD apparatus chamber 10when the protective film is formed on the disk D; and process gas supplysources 14, 14 for supplying process gas serving as a raw material forthe protective film, which film is formed on the disk D.

[0092] The CVD apparatus chamber 10 is connected to feeding pipes 15, 15for feeding process gas from the supply sources 14, 14 into the CVDapparatus chamber 10, and is also connected to a discharge pipe 16 fordischarging gas from the CVD apparatus chamber 10 to the outside. Therespective feeding pipes 15, 15 have process gas flow control valves(not shown in the figure), which control the flow rate of the gas fed tothe CVD apparatus chamber 10 to thereby arbitrarily set the flow rate ofthe gas. The discharge pipe 16 has a discharge amount control valve 17,which controls the discharge amount to thereby arbitrarily set thepressure in the CVD apparatus chamber 10.

[0093] Preferred examples of the high-frequency power sources 12, 12include a power source which can supply power of 50-1,000 W duringformation of the protective film predominantly containing carbon andduring discharge of oxygen plasma. The frequency of the high-frequencypower sources 12, 12 is not particularly specified from the viewpoint ofthe effect of the present invention. For example, the frequency may be13.56 MHz.

[0094] A pulse direct-current power source or a high-frequency powersource may be employed as the bias power source 13.

[0095]FIG. 5 shows a schematic representation of a protective filmmodification apparatus employed for carrying out an embodiment of theproduction process for the magnetic recording medium of the presentinvention. The apparatus includes a chamber 20 for accommodating a diskD having a protective film predominantly containing carbon, which filmis to be modified; and a high-frequency power source 21 for supplyinghigh-frequency power to the disk D in the chamber 20. Reference numeral24 represents a matching apparatus.

[0096] The chamber 20 is connected to a feeding pipe 25 for feedingnitrogen gas from a non-illustrated supply source into the chamber 20,and is also connected to a discharge pipe 26 for discharging gas fromthe chamber 20 to the outside. The discharge pipe 26 has a dischargeamount control valve 27, which controls the discharge amount to therebyarbitrarily set the pressure in the chamber 20.

[0097] Preferred examples of the high-frequency power source 21 includea power source which can supply power of 50-1,000 W during modificationof the protective film. The frequency of the high-frequency power source21 is not particularly specified from the viewpoint of the effect of thepresent invention. The frequency may be an Rf frequency, of, forexample, 13.56 MHz.

[0098] The protective film modification apparatus and the plasma CVDapparatus are connected to each other such that the disk in the plasmaCVD apparatus can be conveyed into the protective film modificationapparatus without the disk being exposed to air. By using the protectivefilm modification apparatus and the plasma CVD apparatus, which areconnected to each other such that the disk D in the plasma CVD apparatuscan be conveyed into the protective film modification apparatus withoutthe disk being exposed to air, deposition of impurities derived from theair onto the protective film can be prevented, and lowering of thebonding force between the protective film and the lubrication film,which lowering is caused by such impurities, can be prevented.

[0099] In the present invention, there may be employed a protective filmmodification apparatus including coils for generating a magnetic fieldin a chamber 20, which coils are provided on outer side walls of thechamber 20.

[0100] When such a protective film modification apparatus is employed,plasma in the chamber 20 is gathered around the disk D by the effect ofthe magnetic field generated by the coils during modification of theprotective film. Therefore, efficiency in modification of the protectivefilm can be enhanced.

[0101] An embodiment of the production process for the magneticrecording medium of the present invention will next be described bytaking, as an example, the case in which the aforementioned apparatus isemployed.

[0102] Firstly, the production process including a step in which aprotective film formed through CVD is subjected to modification will bedescribed.

[0103] (Embodiment 1 of Production Process)

[0104] A non-magnetic undercoat layer 1 and a magnetic layer 2 aresuccessively formed on both surfaces of a non-magnetic substrate Sthrough a technique such as sputtering, vacuum deposition, or ionplating, to thereby obtain a disk D.

[0105] An embodiment of the production process for the disk D will bespecifically described. The non-magnetic substrate S may be an aluminumalloy substrate on which an NiP plating film is formed (hereinafter thesubstrate may be referred to as “NiP-plated Al substrate”), which isgenerally employed as a substrate for magnetic recording media; or asubstrate of glass, ceramic, or flexible resin, which substrate may becoated with NiP or another alloy through plating or sputtering. The meansurface roughness (Ra) of the non-magnetic substrate S is preferably1-20 Å. When the substrate S is subjected to texturing or a similartechnique, a desired mean surface roughness (Ra) can be attained.

[0106] The aforementioned respective layers are formed under, forexample, the sputtering conditions described below. A chamber in whichthe layers are formed is evacuated to 10⁻⁴ to 10⁻⁷ [Pa]. The substrateis placed in the chamber, and then the substrate is heated to, forexample 200-250° C., so as to attain a desired coercive force.Subsequently, Ar gas is introduced into the chamber and discharge iscarried out, to thereby carry out sputtering for film formation. Whensputtering is carried out, power of 0.2-2.0 [kW] is supplied. Thedischarge time and the supply power may be regulated, to thereby attaina desired film thickness.

[0107] The non-magnetic undercoat layer 1 is a conventionally knownnon-magnetic undercoat layer. For example, the layer 1 is a singleelement film formed from any element selected from Cr, Ti, Ni, Si, Ta,and W. Alternatively, the layer 1 is a film formed from an alloycontaining any of the above elements as a primary component and otherelements, so long as such “other elements” do not impede thecrystallinity of the layer 1. The non-magnetic undercoat layer 1 isprovided for controlling the crystal orientation of the magnetic layer 2formed from a Co alloy. The layer 1 is preferably formed from asputtering target containing a material of solely Cr or a materialcontaining Cr and one or more selected from among Mo, W, V, Ti, Nb, andSi. When the aforementioned material is employed, the crystalorientation of the magnetic layer 2 formed from a Co alloy, the layer 2being provided on the non-magnetic undercoat layer 1, is improved, andtherefore the magnetic recording medium exhibits excellent coerciveforce and noise characteristics; i.e., the medium is suitable forrealization of high recording density.

[0108] The crystal grain size of the non-magnetic undercoat layer 1 mayaffect the crystal grain size of the magnetic layer 2 formed from a Coalloy. The crystal grain size of the non-magnetic undercoat layer 1 maybe reduced by employing a sputtering target containing an element suchas B, Zr, or Ta and the material of the layer 1; i.e., Cr or a Cr alloy.

[0109] The thickness of the non-magnetic undercoat layer 1 is notparticularly limited, so long as the thickness falls within a range soas to attain a appropriate coercive force. The thickness is preferably100-1,000 Å, more preferably 150-700 Å. The magnetic recording mediumincluding the non-magnetic undercoat layer 1 having a thickness fallingwithin the above range exhibits enhanced coercive force and improvedSNR; i.e., the medium is suitable for realization of high recordingdensity, which is preferable.

[0110] The non-magnetic undercoat layer 1 may be of a single-layerstructure, or of a multi-layer structure. When the layer 1 has amulti-layer structure, the layer 1 may be formed of a plurality oflayers formed from the same composition or different compositions fromamong the aforementioned compositions. For example, the layer 1 may be amulti-layer structure in which a CrMo alloy layer (Mo content: 10 at %or less) is laminated on a Cr layer.

[0111] The magnetic layer 2 formed from a Co alloy may be formed from amaterial containing any Co alloy composition selected from among Co/Cr,Co/Cr/Ta, Co/Cr/Pt, Co/Cr/Pt/Ta, and the like.

[0112] The thickness of the magnetic layer 2 formed from a Co alloyfalls within a range of 30-100 [Gμm], which is a parameter ofconventionally used Brd (the product of residual magnetization and filmthickness [Gμm]), and the thickness of the layer 2 may be regulated soas to attain an appropriate recording and reproducing signal output.

[0113] In order to carry out film formation efficiently andconsistently, if necessary, a bias of −200 to −400 [V] is preferablyapplied to the non-magnetic substrate S during formation of thenon-magnetic undercoat layer 1 and the magnetic layer 2.

[0114] In order to improve the orientation of the Co alloy and to obtainhigh coercive force, a non-magnetic intermediate layer may be providedbetween the non-magnetic undercoat layer 1 and the magnetic layer 2. Forexample, a CoCr alloy layer (Cr content: 50 at % or less) having athickness of 25 Å or less may be formed.

[0115] The formation process for a protective film will next bedescribed.

[0116] The disk D including the substrate S, the undercoat layer 1, andthe magnetic layer 2 is conveyed to a predetermined position in the CVDapparatus chamber 10 by means of an unillustrated conveying apparatus.Meanwhile, a reaction gas supplied from the supply source is fed throughthe feeding pipes 15, 15 into the CVD apparatus chamber 10, and theexisting gas in the CVD chamber 10 is discharged through the dischargepipe 16. Thus, the reaction gas is passed throughout the CVD apparatuschamber 10, to thereby expose the surfaces of the disk D to the reactiongas.

[0117] The reaction gas may be a hydrocarbon-containing gas; forexample, a gas containing, as a primary component, a gas mixture ofhydrocarbon and hydrogen. In the gas mixture, the volume ratio ofhydrocarbon to hydrogen is preferably set at 2:1-1:100, in order toobtain a harder and more durable protective film predominantlycontaining carbon. As used herein, the term “a gas containing a gasmixture as a primary component” refers to the gas mixture beingcontained in the gas in an amount of 90 vol % or more.

[0118] One or more selected from among lower saturated hydrocarbons,lower unsaturated hydrocarbons, and lower cyclic hydrocarbons arepreferably employed as the aforementioned hydrocarbon. Examples of lowersaturated hydrocarbons which may be employed include methane, ethane,propane, butane, and octane. Examples of lower unsaturated hydrocarbonswhich may be employed include isoprene, ethylene, propylene, butylene,and butadiene. Examples of lower cyclic hydrocarbons which may beemployed include benzene, toluene, xylene, styrene, naphthalene,cyclohexane, and cyclohexadiene. As used herein, the term “lowerhydrocarbon” refers to a hydrocarbon of C1-C10.

[0119] A lower hydrocarbon is preferably employed as the hydrocarbon,for the reasons described below. When the number of carbons in thehydrocarbon is in excess of the upper limit of the aforementioned range,the hydrocarbon becomes difficult to feed in the form of gas, and thehydrocarbon is not easily decomposed during discharge. As a result, theprotective film predominantly containing carbon contains a large amountof polymer components having poor strength.

[0120] In the formation process, the pressure in the CVD chamber 10 ispreferably adjusted to fall within a range of 0.1-10 Pa, byappropriately controlling the discharge rate of the gas from the chamber10 by use of the discharge amount control valve 17. In addition, theflow rate of the reaction gas is preferably 50-500 sccm.

[0121] Simultaneously, high-frequency power, preferably 50-2,000 W, issupplied to the electrodes 11, 11 by use of the high-frequency powersources 12, 12, to thereby generate plasma in the chamber. A protectivefilm predominantly containing carbon is formed on each surface of thedisk D through plasma chemical vapor deposition making use of theaforementioned reaction gas serving as a raw material.

[0122] The thickness of the protective film is 30-100 Å, preferably30-75 Å. When power is supplied to the electrodes 11, 11, the phases ofpower supplied to the electrodes 11, 11 are preferably different fromeach other. This is because the rate of film formation and durability ofthe protective film can be improved when the phases are different. Thedifference between the phases of power supplied to the electrodes 11, 11is preferably 90-270°, more preferably 180°0 (opposite phase).

[0123] Alternatively, the protective film predominantly containingcarbon may be formed through usually employed CVD.

[0124] When the protective film is formed by use of the plasma CVDapparatus, the film contains a large amount of a diamond-like carbon(hereinafter referred to as “DLC”) component having high hardness, andthus the protective film exhibits excellent strength. Active portions onthe surface of the thus-formed carbon protective film are hydrogenated,and thus the film contains a large amount of C—H bonds that are noteasily polarized; i.e., the chemical activity of the surface of the filmis low.

[0125] In the production process of the embodiment, the disk D on whichthe carbon protective film is formed is conveyed into the chamber 20 ofthe protective film modification apparatus shown in FIG. 5, and thecarbon protective film is subjected to etching by use of a protectivefilm modification gas under conditions such that the extraction amountof an inspection gas component and/or a compound component formed so asto contain the inspection gas component is equal to or greater than acertain threshold, the gas component and/or the compound component beingextracted with an inspection solvent after the carbon protective film isallowed to stand in an atmosphere of the inspection gas component, tothereby produce a magnetic recording medium in which the protective filmhas undergone modification. When the extracted component is melamine,the threshold is preferably determined to be 0.06 [μg/100 cm²], morepreferably 0.12 [μg/100 cm²], much more preferably 0.24 [μg/100 cm²].

[0126] As used herein, the term “protective film modification” refers tothe protective film being subjected to etching under conditions suchthat the extraction amount of an inspection gas component and/or acompound component formed so as to contain the inspection gas componentis equal to or greater than a certain threshold, the gas componentand/or the compound component being extracted with an inspection solventafter the carbon protective film is allowed to stand in an atmosphere ofthe inspection gas component.

[0127] The protective film modification gas may contain one or moreselected from among Ar gas, oxygen gas, and nitrogen gas.

[0128] According to the magnetic recording medium including the carbonprotective film which has been modified through protective filmmodification, the extraction amount is equal to or greater than thethreshold, and thus the amount of the inspection gas adsorbed in theprotective film is large. The reason for this is thought to be asfollows.

[0129] When the protective film is exposed to plasma of the protectivefilm modification gas through protective film modification, a largenumber of C—H bonds present in the carbon protective film are cleaved bythe plasma, and the resultant C atoms are bonded to nitrogen. Inaccordance with the type of the employed modification gas, a C—O bond, aC═O bond, a C═C bond, a C≡C bond, a C═N bond, a C≡N bond, or a similarbond is formed. These bonds are considered to have high chemicalactivity. The inspection gas is considered to be adsorbed onto such ahighly active site. Meanwhile, from the surface to the inside of theprotective film exposed to the modification gas, micropores are thoughtto be formed by the effect of the modification gas. Since the microporescause an increase in the effective surface area of the protective filmin relation to adsorption, the protective film exhibits characteristicso as to increase the adsorption amount of the inspection gas.

[0130] Therefore, the amount of the inspection gas adsorbed in thecarbon protective film which has undergone modification increases. Inaddition, the amount of the inspection gas adsorbed in the carbonprotective film which has undergone modification satisfactorily isthought be equal to or greater than the threshold.

[0131] While the protective film modification gas supplied from anon-illustrated source is introduced into the chamber through thefeeding pipe, the existing gas in the chamber is discharged through thedischarge pipe, and the modification gas is passed throughout thechamber, to thereby expose to the protective film modification gas thesurface of the carbon protective film formed on each of the surfaces ofthe disk.

[0132] During protective film modification, the pressure in the chamberis preferably adjusted to fall within a range of 2.4-8 Pa (morepreferably 2.4-6 Pa), by appropriately controlling the discharge amountof the gas from the chamber by use of the discharge amount controlvalve. When the pressure in the chamber is below the above range,modification of the surface of the protective film is unsatisfactory,and thus the amount of deposits adsorbed in the film does not increase,and deposits are easily deposited onto the surface of the film. Incontrast, when the pressured in the chamber is in excess of the aboverange, the surface of the protective film becomes chemically unstable,and thus durability of the film may be lowered.

[0133] During protective film modification, high-frequency power ofpreferably 30-500 W (more preferably 30-300 W, much more preferably30-200 W) is supplied to the electrodes by use of the high-frequencypower supply, to thereby generate plasma of the aforementioned nitrogengas serving as a raw material. The surface of the carbon protective filmof the disk is subjected to modification by use of the resultant plasma.

[0134] When the power supplied to the disk is below the above range,modification of the surface of the protective film is unsatisfactory,and thus the amount of deposits adsorbed in the film does not increase,and deposits are easily deposited onto the surface of the film. Incontrast, when the power is in excess of the above range, the surface ofthe protective film becomes chemically unstable, and thus durability ofthe film may be lowered.

[0135] The time for protective film modification is 2-6 seconds,preferably 3-5 seconds. When the time for protective film modificationis below the above range, modification of the surface of the protectivefilm is unsatisfactory, and thus the amount of deposits adsorbed in thefilm does not increase, and deposits are easily deposited onto thesurface of the film. In contrast, when the modification time is inexcess of the above range, the surface of the protective film becomeschemically unstable, and thus durability of the film may be lowered.

[0136] The protective film predominantly containing carbon is subjectedto modification under conditions such that the intensity of the peakcorresponding to a carbon-hydrogen bond of the infrared spectrum of thesurface of the film is preferably 0.055 or less, more preferably 0.05 orless, much more preferably 0.04 or less. This is because, when alubricant is applied onto such a modified protective film predominantlycontaining carbon, bonding between the film and the lubricant can bestrengthened, and deposition of the lubricant onto a magnetic head canbe suppressed.

[0137] When the protective film is subjected to modification, the powersupplied to the disk, the modification time, or the pressure in thechamber is regulated, to thereby control the water contact angle of thesurface of the protective film. The water contact angle of the surfaceof the protective film is preferably 80° or less, more preferably 75° orless. This is because, when the water contact angle is 80° or less, theprotective film is satisfactorily bonded to the lubricant, and thus thelubricant is not easily deposited onto a magnetic head.

[0138] When impurities that induce deposition of deposits onto thesurface of the protective film are deposited onto the film after thefilm is formed on the disk in the plasma CVD apparatus, the impuritiesare removed from the surface of the protective film by plasma generatedfrom the protective film modification gas during protective filmmodification. Therefore, deposits are not easily deposited onto theprotective film.

[0139] When nitrogen gas is employed as the protective film modificationgas, plasma is generated from the nitrogen gas by power supplied to theelectrodes, and bonds in the carbon protective film are cleaved by theresultant plasma, to thereby form a carbon nitride compound, which ispreferable. The reason why nitrogen gas is employed as the protectivefilm modification gas is that the carbon protective film is easilydesigned; i.e., variance in the thickness of the protective film can besuppressed, since a compound which is easily gasified is not easilyformed when nitrogen gas is bonded to the component of the protectivefilm. When the protective film is subjected to modification, themodification conditions are determined such that the ratio of nitrogento carbon in the protective film, as measured by means of ESCA, ispreferably 5-40%, more preferably 5-25%, much more preferably 13-25%.When the ratio of nitrogen to carbon is below the above range,modification of the surface of the protective film is unsatisfactory,and thus the amount of deposits adsorbed in the film does not increase,and deposits are easily deposited onto the surface of the film. Inaddition, the activity of the surface of the protective film is lowered,bonding between the film and the lubricant is weakened, the lubricant iseasily deposited onto a magnetic head, and thus fly stictioncharacteristic is impaired, which is not preferable.

[0140] When the carbon protective film is subjected to modification byuse of nitrogen gas, the film is preferably subjected to modificationunder conditions such that the protective film contains nitrogen in anamount of 2 at % or less in the vicinity of a surface of the film, thesurface being brought into contact with the magnetic layer. This isbecause, when the amount of nitrogen falls outside the above range,magnetostatic characteristics of the magnetic layer deteriorate andcoercive force is lowered, and thus the magnetic recording medium is notsuitable for realization of low flying height.

[0141] According to the protective film predominantly containing carbonformed in the CVD apparatus, the Id/Ig value as measured through Ramanspectroscopy is 3.5 or less. Therefore, the protective film is subjectedto modification under conditions such that the Id/Ig value is preferably3.5 or less, more preferably 3.0 or less, much more preferably 2.5 orless.

[0142] Subsequently, a lubricant such as perfluoropolyether is appliedonto the protective film through, for example, dipping, to thereby forma lubrication film and produce a magnetic recording medium. Thelubrication film formed on the protective film is strongly bonded to thesurface of the protective film. The lubrication film is formed on theprotective film predominantly containing carbon. The lubrication film isformed by applying a lubricant onto the protective film through aconventionally known technique such as dipping or spin coating. Thelubricant may be a material containing any lubricant selected from amonga Fomblin-type lubricant, a Gaudi-type lubricant, a Demnum-typelubricant, and a Krytox-type lubricant.

[0143] (Embodiment 2 of Production Process)

[0144] Another embodiment of the production process for the magneticrecording medium will next be described by taking, as an example, thecase in which protective film modification is not carried out.

[0145] The disk D including the substrate S, the undercoat layer 1, andthe magnetic layer 2 is conveyed to a predetermined position in the CVDapparatus chamber 10 by means of an unillustrated conveying apparatus.Meanwhile, a reaction gas supplied from the supply source is fed throughthe feeding pipes 15, 15 into the CVD apparatus chamber 10, and theexisting gas in the chamber 10 is discharged through the discharge pipe16. Thus, the reaction gas is passed throughout the CVD apparatuschamber 10, to thereby expose the surfaces of the disk D to the reactiongas.

[0146] When a protective film predominantly containing carbon is formedin a manner similar to that described above, the film may be formedwhile pulse direct-current bias is applied to the disk D, in order toincrease the amount of deposits adsorbed in the film; i.e., in order tocause the extraction amount of the deposits to at least a certainthreshold. When the protective film is formed while pulse direct-currentbias is applied to the disk D, the extraction amount of an inspectiongas component and/or a compound component formed so as to contain theinspection gas component becomes equal to or greater than a certainthreshold, the gas component and/or the compound component beingextracted with an inspection solvent after the carbon protective film isallowed to stand in an atmosphere of the inspection gas component. Theprotective film is formed while pulse direct-current bias is applied tothe disk D, so as to attain a threshold (in the case in which theextracted component is melamine) of preferably 0.06 [μg/100 cm²], morepreferably 0.12 [μg/100 cm²], much more preferably 0.24 [μg/100 cm²].

[0147] When bias is applied to the disk, plasma sufficiently impinges onthe surface of the disk, and thus the temperature of the disk iselevated and a carbon-hydrogen bond is dissociated. In addition, whenplasma impinges directly on the surface of the disk, the carbon-hydrogenbond is easily dissociated; i.e., the carbon-hydrogen bond isefficiently dissociated, and thus the amount of deposits adsorbed in theprotective film can be increased. According to a conventionalacceleration method in which grid voltage is applied in thermionicemission plasma generation, a carbon-hydrogen bond is not dissociatedwhen plasma impinges directly on the surface of the disk D, and thus theamount of deposits adsorbed in the protective film cannot be increased.When bias is applied to the disk D, the bias may be applied directly tothe disk D, or may be applied to the disk D via a non-illustrated diskcarrier (i.e., an apparatus for carrying and conveying the disk D).

[0148] The pulse direct-current bias applied to the disk D has a meanvoltage of −450 to −60 V, preferably −400 to −150 V, more preferably−350 to −200 V.

[0149] When the mean voltage is below the lower limit of the aboverange, plasma impinges on the surface of the disk D very strongly tothereby hinder activated species of the reaction gas excited by plasmafrom depositing on the disk D. As a result, the protective filmpredominantly containing carbon tends to have insufficient density andpoor sliding durability.

[0150] In contrast, when the mean voltage is in excess of the upperlimit of the above range, plasma impinges on the surface of the disk Dvery weakly, and modification of the protective film is unsatisfactory,and thus the amount of deposits adsorbed in the film does not increase;i.e., the deposits are easily deposited onto the surface of the film.

[0151] When the protective film predominantly containing carbon isformed, the temperature of the substrate is determined at 130° C. orhigher, preferably 150° C. or higher, more preferably 170° C. or higher.When the temperature of the substrate is below the lower limit of theabove range, the heat quantity of the substrate is small, and thusdissociation of a carbon-hydrogen bond by the heat (i.e., heatelimination of hydrogen) does not easily occur. As a result,modification of the protective film is unsatisfactory, and thus theamount of deposits adsorbed in the film does not increase; i.e., thedeposits are easily deposited onto the surface of the film.

[0152] As described above, when the mean voltage of the pulsedirect-current bias falls within the above range, plasma impinges on thesurface of the disk D appropriately. In addition, when the temperatureof the substrate falls within the above range, dissociation of acarbon-hydrogen bond (i.e., heat elimination of hydrogen) easily occurs.As a result, modification of the protective film is satisfactory, andthus the amount of deposits adsorbed in the film increases; i.e., thedeposits are not easily deposited onto the surface of the film.

[0153] Moreover, the bias is applied to the disk D under conditions suchthat the intensity of the peak corresponding to a carbon-hydrogen bondof the infrared spectrum of the surface of the protective film ispreferably 0.055 or less, more preferably 0.05 or less, much morepreferably 0.04 or less. This is because, when a lubricant is appliedonto such a protective film predominantly containing carbon, bondingbetween the film and the lubricant can be strengthened, and depositionof the lubricant onto a magnetic head can be suppressed.

[0154] When the protective film predominantly containing carbon isformed, a high-frequency power source may be employed as the bias powersource 13, and instead of pulse direct-current bias, high-frequency biasmay be applied to the disk. In this case, the high-frequency powerapplied to the disk is 10-300 W, preferably 10-150 W. The frequency maybe an Rf frequency, of, for example, 13.56 MHz.

[0155] The aforementioned pulse direct-current bias has a positivevoltage peak value; i.e., a peak value in a positive region of a pulseportion, of 10-100 V, preferably 20-75 V. When the peak value is belowthe lower limit of the above range, a positive bias voltage cannotsufficiently cancel negative charges accumulated on the surface of thedisk, and deposition of the activated species on the disk is hindered.As a result, the protective film predominantly containing carbon tendsto have insufficient density and poor sliding durability.

[0156] The positive voltage peak value of the pulse direct-current bias,the pulse width, and the frequency are regulated such that the Id/Igvalue in relation to the protective film predominantly containingcarbon, which value is obtained through Raman spectroscopy, ispreferably 3.5 or less, more preferably 3.0 or less, much morepreferably 2.5 or less.

[0157] When the positive voltage peak value is in excess of the upperlimit of the above range, reverse-sputtering tends to occur on the diskD and the protective film predominantly containing carbon tends to haveinsufficient density and poor sliding durability.

[0158] Thus, when the positive voltage peak value of the pulsedirect-current bias falls within the above range, a positive biasvoltage can cancel negative charges accumulated on the surface of thedisk, and can promote the deposition of the activated species on thedisk. As a result, the protective film predominantly containing carbonbecomes dense and improves in sliding durability.

[0159] The pulse direct-current bias has a frequency of 1 kHz-100 GHz,preferably 10 kHz-1 GHz. When the frequency is below the lower limit ofthe above range, a positive bias voltage cannot sufficiently cancelnegative charges accumulated on the surface of the disk D, anddeposition of the activated species on the disk D is hindered. As aresult, the protective film predominantly containing carbon tends tohave insufficient density and poor sliding durability. In contrast, whenthe frequency is in excess of the upper limit of the above range,reverse-sputtering tends to occur on the surface of the disk D and theprotective film tends to have insufficient density and poor slidingdurability.

[0160] The pulse direct-current bias has a pulse width of 1 ns-500 μs,preferably 10 ns-50 μs. When the pulse width is below the lower limit ofthe above range, a positive bias voltage cannot sufficiently cancelnegative charges accumulated on the surface of the disk D, anddeposition of the activated species on the disk D is hindered. As aresult, the protective film predominantly containing carbon tends tohave insufficient density and poor sliding durability. In contrast, whenthe pulse width is in excess of the upper limit of the above range,reverse-sputtering tends to occur on the surface of the disk D and theprotective film tends to have insufficient density and poor slidingdurability.

[0161] As used herein, the term “positive voltage peak value of pulsedirect-current bias” refers to, for example, a peak value X in apositive region in a pulse portion of a voltage waveform of a pulsedirect-current bias shown in FIG. 7. In this case, a pulse width refersto a width Y in the pulse portion.

[0162] When the protective film is formed through application of bias,conditions of applied bias are controlled, as are other conditions suchas the treatment time and the pressure in the chamber, to therebycontrol the water contact angle of the surface of the protective film.The water contact angle of the surface of the protective film ispreferably 80° or less, more preferably 75° or less. This is because,when the water contact angle is 80° or less, the protective film issatisfactorily bonded to the lubricant, and thus the lubricant is noteasily deposited onto a magnetic head.

[0163] In a manner similar to that described above, a lubrication filmis formed on the protective film predominantly containing carbon, whichis formed on the disk.

[0164] (Embodiment 3 of Production Process)

[0165] Another embodiment of the production process for the magneticrecording medium will next be described by taking, as an example, thecase in which sputtering is carried out in combination with applicationof bias.

[0166] After the disk D is obtained in a manner similar to thatdescribed above, a protective film is formed as described below.

[0167] In the production process of the embodiment, a disk D2—which isobtained by forming a carbon protective film on the disk D through CVDin a manner similar to that of any of the aforementioned embodiments—isconveyed into a sputtering chamber including a sputtering targetcontaining a carbon-containing material and having means for introducinginto the chamber, as a sputtering gas, Ar gas or a gas mixturecontaining Ar gas and nitrogen gas, and plasma of the gas is generatedthrough discharge, to thereby form another protective film predominantlycontaining carbon on the surface of the disk D2 through sputtering.During sputtering, bias is applied to the disk under conditions suchthat the extraction amount of an inspection gas component and/or acompound component formed so as to contain the inspection gas componentis equal to or greater than a certain threshold, the gas componentand/or the compound component being extracted with an inspection solventafter the carbon protective film is allowed to stand in an atmosphere ofthe inspection gas component, to thereby form the protective film. Whenthe extracted component is melamine, the threshold is preferablydetermined to be 0.06 [μg/100 cm²], more preferably 0.12 [μg/100 cm²],much more preferably 0.24 [μg/100 cm²]. The protective film may beformed by use of the apparatus shown in FIG. 6. In FIG. 6, referencenumerals 41 and 42 represent sputtering targets, and reference numeral21 represents a bias power supply for applying bias to the disk D2.

[0168] When the protective film predominantly containing carbon isformed through sputtering while bias is applied to the disk, theprotective film is formed while the surface of film is impinged withplasma. In addition, the protective film formed on the disk through CVDis modified. As a result, the thus-formed film has a large amount ofmicropores; i.e., the film has a large effective area in relation toadsorption, and thus the film can adsorb a sufficient amount of depositstherein.

[0169] According to the magnetic recording medium produced as descriedabove, the extraction amount of an inspection gas component and/or acompound component formed so as to contain the inspection gas componentis equal to or greater than a certain threshold, the gas componentand/or the compound component being extracted with an inspection solventafter the medium is allowed to stand in an atmosphere of the inspectiongas component.

[0170] The high-frequency power applied to the disk is 100-400 W,preferably 100-200 W. The frequency may be an Rf frequency, of, forexample, 13.56 MHz. When the high-frequency power falls within the aboverange, the protective film has a sufficient amount of micropores, andthus the film can adsorb a sufficient amount of deposits therein.

[0171] A pulse direct-current bias similar to that shown in FIG. 7 maybe applied to the disk. The pulse direct-current bias applied to thedisk D preferably has a mean voltage of −450 to −60 V, more preferably−400 to −150 V, much more preferably −350 to −200 V. When the meanvoltage of the pulse direct-current bias falls within the above range,plasma impinges on the surface of the disk D appropriately, and thus theresultant protective film has a large effective surface area in relationto adsorption. As a result, the amount of deposits adsorbed in the filmincreases, and the deposits are not easily deposited onto the surface ofthe film.

[0172] The temperature of the substrate is preferably 130° C. or higher,more preferably 150° C. or higher. When the temperature of the substratefalls within the above range, the resultant protective film has a largeeffective surface area in relation to adsorption. As a result, theamount of deposits adsorbed in the film increases, and the deposits arenot easily deposited onto the surface of the film.

[0173] The aforementioned pulse direct-current bias has a positivevoltage peak value; i.e., a peak value in a positive region of a pulseportion, of 10-100 V, preferably 20-75 V. The pulse direct-current biashas a frequency of 1 kHz-100 GHz, preferably 10 kHz-1 GHz. The pulsedirect-current bias has a pulse width of 1 ns-500 μs, preferably 10ns-50 μs. When the positive voltage peak value, the frequency, and thepulse width fall within the above ranges, plasma impinges on the surfaceof the disk D appropriately, and thus the resultant protective film hasa large effective surface area in relation to adsorption. As a result,the amount of deposits adsorbed in the film increases, and the depositsare not easily deposited onto the surface of the film.

[0174] When a gas mixture containing Ar gas and nitrogen gas is employedas a sputtering gas, the conditions for sputtering are preferablydetermined such that the ratio of nitrogen to carbon contained in theprotective film, as measured by means of ESCA, is preferably 5-40%, morepreferably 5-25%, much more preferably 13-25%. When the ratio ofnitrogen to carbon is below the above range, modification of the surfaceof the protective film is unsatisfactory, and thus the amount ofdeposits adsorbed in the film does not increase, and deposits are easilydeposited onto the. surface of the film. In addition, the activity ofthe surface of the protective film is lowered, bonding between the filmand the lubricant is weakened, the lubricant is easily deposited onto amagnetic head, and thus fly stiction characteristic is impaired, whichis not preferable.

[0175] When a gas mixture containing Ar gas and nitrogen gas is employedas a sputtering gas, preferably, the protective film predominantlycontaining carbon has a carbon nitride compound on a first surfacethereof, the surface being opposite the magnetic layer, and theprotective film contains nitrogen in an amount of 2 at % or less in thevicinity of a second surface thereof, the surface being brought intocontact with the magnetic layer. This is because, when the amount ofnitrogen falls outside the above range, coercive force, which is one ofmagnetostatic characteristics, is lowered, and thus the magneticrecording medium is not suitable for realization of low flying height.

[0176] When the protective film is formed through sputtering, otherconditions for sputtering are determined, for example, as describedbelow. The chamber in which the film is formed is evacuated to 10⁻⁴ to10⁻⁷ [Pa]. The substrate which has been heated in the previous step isplaced in the chamber. While Ar gas and nitrogen gas are introduced intothe chamber so as to attain a pressure of 0.5-1.0 [Pa], plasma isgenerated through discharge, and a target containing a carbon-containingmaterial is employed as a raw material, to thereby form a film throughsputtering. During sputtering, power of 0.2-2.0 [kW] is supplied. Theprotective film having a desired thickness may be formed by regulatingthe discharge time and the power which is supplied. When the protectivefilm is formed through sputtering, the power which is supplied is0.2-2.0 [kW], preferably 0.7-1.8 [kW]. When the power is less than 0.2[kW], a satisfactory thickness is not attained, whereas when the poweris in excess of 2.0 [kW], the protective film formed through sputteringmay have low density. In addition, when the power is in excess of 2.0[kW], a carbon nitride compound formed through sputtering diffuses inthe protective film in a direction toward the magnetic layer, and theprotective film may contain nitrogen in an amount of more than 2 at % inthe vicinity of a surface thereof, the surface being brought intocontact with the magnetic layer.

[0177] The carbon protective film formed through CVD, the film beingincluded in the disk D2, preferably has a thickness of 10-60 Å. This isbecause, when the thickness is less than 10 Å, satisfactory strength isnot obtained, and a carbon nitride compound formed through sputteringdiffuses in the protective film in a direction toward the magneticlayer, and the protective film may contain nitrogen in an amount of morethan 2 at % in the vicinity of a surface thereof, the surface beingbrought into contact with the magnetic layer.

[0178] The protective film predominantly containing carbon is formedthrough sputtering under conditions such that the intensity of the peakcorresponding to a carbon-hydrogen bond of the infrared spectrum of thesurface of the protective film is preferably 0.055 or less, morepreferably 0.05 or less, much more preferably 0.04 or less. This isbecause, when a lubricant is applied onto such a protective filmpredominantly containing carbon, bonding between the film and thelubricant can be strengthened, and deposition of the lubricant onto amagnetic head can be suppressed.

[0179] When the protective film is formed through sputtering while biasis applied to the disk, conditions of applied bias, sputteringconditions, and other conditions such as treatment time and pressure inthe chamber are regulated, to thereby control the water contact angle ofthe surface of the protective film. The water contact angle of thesurface of the protective film is preferably 80° or less, morepreferably 75° or less. This is because, when the water contact angle is80° or less, the protective film is satisfactorily bonded to thelubricant, and thus the lubricant is not easily deposited onto amagnetic head.

[0180] In a manner similar to that described above, a lubrication filmis formed on the protective film predominantly containing carbon, whichis formed on the disk.

[0181] (Another Embodiment of the Production Process)

[0182] In the aforementioned embodiment 3 of the production process, aprotective film may be formed through a conventional sputtering process,instead of through the CVD process.

[0183] Since a film similar to that formed in the embodiment 3 is formedon the surface of the protective film, the aforementioned effect may beobtained.

[0184] Alternatively, in the aforementioned embodiment 3 of theproduction process, instead of a protective film being formed throughCVD, a protective film may be formed through sputtering while bias isapplied. Since a film similar to that formed in the embodiment 3 isformed on the surface of the protective film, the aforementioned effectmay be obtained. When a gas mixture containing Ar gas and nitrogen gasis employed as a sputtering gas, preferably, the protective filmpredominantly containing carbon has a carbon nitride compound on a firstsurface thereof, the surface being opposite to the magnetic layer, andthe protective film contains nitrogen in an amount of 2 at % or less inthe vicinity of a second surface thereof, the surface being brought intocontact with the magnetic layer. This is because, when the amount ofnitrogen falls outside the above range, coercive force, which is one ofmagnetostatic characteristics, is lowered, and thus the magneticrecording medium is not suitable for realization of low flying height.In order to avoid such a problem, for example, the protective film maybe firstly formed by use of a gas containing no nitrogen gas, and thenformed by use of a gas containing nitrogen gas.

[0185] According to the magnetic recording medium produced through theproduction process of the aforementioned embodiment, the extractionamount of an inspection gas component and/or a compound component formedso as to contain the inspection gas component is equal to or greaterthan a certain threshold, the gas component and/or the compoundcomponent being extracted with an inspection solvent after the carbonprotective film is allowed to stand in an atmosphere of the inspectiongas component. Therefore, the protective film predominantly containingcarbon of the magnetic recording medium is not prone to have deposits onits surface. When the extracted component is melamine, the threshold ispreferably 0.06 [μg/100 cm²]. Since deposits are not deposited onto amagnetic head even when the flying height of the head is reduced, flystiction characteristic of the magnetic recording medium is not impairedeven in the case in which the flying height of the head is reduced. Whenthe carbon protective film is subjected to FTIR, the intensity of thepeak corresponding to a carbon-hydrogen bond is preferably 0.055 orless. Therefore, the surface of the protective film is consistentlycoated with a lubricant, and thus deposition of deposits can besuppressed. The carbon protective film 3 contains nitrogen, and theratio of nitrogen to carbon as measured by means of ESCA is preferably5-40%. Therefore, the film is dense and hard. Preferably, the magneticrecording medium of the present invention includes the protective filmpredominantly containing carbon, which film is hard and thin, exhibitsexcellent sliding durability and lubricity, and suppresses generation ofwear powder, inducing deposition of deposits and generation of Nicorrosion.

[0186] According to the present invention, there can be produced amagnetic recording medium which enables reduction in spacing loss, whichmedium is applicable to realization of high recording density, ascompared with a conventional magnetic recording medium.

[0187] When the magnetic recording medium produced through the processaccording to the present invention is employed, the flying height of amagnetic head can be reduced, and thus the coercive force (Hc) of themedium is preferably enhanced so as to be commensurate with the flyingheight. In order to realize high recording density, the coercive forceof the medium is 3,000 oersteds or more, preferably 3,500 oersteds ormore. A desired coercive force can be attained by regulating thecomposition of the aforementioned undercoat layer and magnetic layer,film thickness, film structure, and film formation conditions, withinthe aforementioned ranges.

[0188] A magnetic recording medium which is not prone to have depositson its surface can be easily produced when the medium is produced suchthat the extraction amount in relation to the medium is equal to orgreater than a certain threshold that has been determined through apretest; for example, when the medium is produced such that theextraction amount in relation to the medium is equal to or greater thanthe extraction amount in relation to a magnetic recording medium whichhas deposits on its surface during a fly stiction test. The degree ofdifficulty in deposition of deposits can be determined through theinspection method of the present invention, and thus the degree can beused as an index for controlling production of a magnetic recordingmedium which is not prone to have deposits on its surface. When theindex is used, the production process is appropriately controlled, andthus such a magnetic recording medium can be easily produced.

[0189] According to the inspection method of the present invention, thedegree of difficulty in deposition of deposits onto the protective filmcan be acceleratedly inspected with in a short period of time.Therefore, the inspection results can be reflected in the productionprocess for a magnetic recording medium within a short period of time,without inspection for generation of deposits on a magnetic recordingmedium which has been practically used for a prolonged period of time.Thus, a magnetic recording medium can be produced to have consistentcharacteristics.

[0190] Therefore, a magnetic recording medium—which exhibits excellentfly stiction characteristic, enables reduction in flying height, and issuitable for realization of high recording density—can be easilyproduced.

[0191] The present invention will next be described in more detail byway of examples, which should not be construed as limiting the inventionthereto.

EXAMPLE 1

[0192] (A Protective Film is Subjected to Modification by Use ofNitrogen Gas after the Film is Formed Through CVD)

[0193] A surface of an NiP-plated Al substrate (diameter: 95 mm,thickness: 0.8 mm) was subjected to texturing so as to attain a meansurface roughness (Ra) of 6 Å, and then the substrate was placed in achamber of a film formation apparatus (model: 3010, product of ANELVA) .After the chamber was evacuated to 2.0×10⁻⁶ Pa, a non-magnetic undercoatlayer (thickness: 350 Å) was formed on the substrate from Cr. On theundercoat layer, a magnetic film (thickness: 250 Å) was formed from aCo16Cr6Pt3Ta layer (Cr content: 16 at %, Pt content: 6 at %, Ta content:3 at %, Co: balance). Before formation of the non-magnetic undercoatlayer, the substrate was heated by use of a heater such that thetemperature of the substrate was 150° C. during formation of aprotective film predominantly containing carbon. The temperature of thesubstrate was measured by use of a radiation thermometer, and wasverified through a window of the chamber immediately before formation ofthe protective film.

[0194] Subsequently, a disk D produced as described above was conveyedinto a CVD apparatus. A hydrogenated carbon film (thickness: 50 Å),serving as the protective film predominantly containing carbon, wasformed on the magnetic film. When the protective film was formed,high-frequency power (frequency: 13.56 MHz) was applied to electrodes,to thereby generate plasma. During formation of the protective film,application of pulse direct-current bias was carried out. The conditionsfor application of pulse direct-current bias are shown in Table 1.

[0195] Subsequently, the disk D on which the carbon protective film wasformed was conveyed into a chamber 20 of a protective film modificationapparatus, and nitrogen gas serving as a protective film modificationgas was supplied to the chamber 20. Simultaneously, high-frequency power(frequency: 13.56 MHz) was applied to the disk D, to thereby generateplasma, and then the carbon protective film formed on each surface ofthe disk D was subjected to modification.

[0196] The conditions for modification are shown in Table 1.

[0197] Subsequently, a Fomblin-type lubricant (Zdol2000, product ofAusimont) was applied onto the protective film through dipping so as toattain a thickness of about 15 Å, to thereby form a lubrication layer onthe protective film predominantly containing carbon.

EXAMPLE 2

[0198] (A Protective Film is Subjected to Modification by Use of OxygenGas after the Film is Formed Through CVD)

[0199] The procedure of Example 1 was repeated, except that theconditions in relation to the protective film modification gas werechanged as shown in Table 1, to thereby produce a magnetic recordingmedium.

EXAMPLE 3

[0200] (A Protective Film was Subjected to Modification by Use of Ar Gasafter the Film is Formed Through CVD)

[0201] The procedure of Example 1 was repeated, except that theconditions in relation to the protective film modification gas werechanged as shown in Table 1, to thereby produce a magnetic recordingmedium.

EXAMPLES 4 THROUGH 7

[0202] (After a Protective Film is Formed Through CVD, AnotherProtective Film is Formed Through Sputtering by Use of Nitrogen Gas andAr Gas)

[0203] A disk D was produced in a manner similar to that described inExample 1.

[0204] Subsequently, the disk D was conveyed into a CVD apparatus, and ahydrogenated carbon film (thickness: 40 Å), serving as the protectivefilm predominantly containing carbon, was formed on the magnetic film.When the protective film was formed, high-frequency power (frequency:13.56 MHz, power: 750 W) was applied to electrodes, to thereby generateplasma. During formation of the protective film, application of pulsedirect-current bias was carried out.

[0205] On the protective film, a protective film containing a carbonnitride compound was formed through sputtering. In Examples 4 and 5, thefilm was formed while high-frequency bias (frequency: 13.56 MHz) wasapplied to the disk. In Examples 6 and 7, the film was formed whilepulse direct-current bias was applied to the disk. The thickness of theprotective film formed through sputtering was 10 Å. The thickness of theprotective film formed through CVD was 40 Å. The conditions forformation of the protective film through sputtering are shown in Table1.

EXAMPLES 8 THROUGH 13

[0206] (A Protective Film is Formed Through CVD with Application ofPulse Direct-current Bias)

[0207] A disk D was produced in a manner similar to that described inExample 1.

[0208] Subsequently, the disk D was conveyed into a CVD apparatus, and ahydrogenated carbon film (thickness: 50 Å), serving as the protectivefilm predominantly containing carbon, was formed on the magnetic film.When the protective film was formed, high-frequency power (frequency:13.56 MHz) was applied to electrodes, to thereby generate plasma. InExamples 8 through 11, the protective film was formed while pulsedirect-current bias was applied to the disk. In Examples 12 and 13, theprotective film was formed while high-frequency bias (frequency: 13.56MHz) was applied to the disk. The conditions for formation of theprotective film are shown in Table 2. Subsequently, a lubrication layerwas formed in a manner similar to that described in Example 1.

EXAMPLES 14 THROUGH 16, COMPARATIVE EXAMPLE 1

[0209] (A Protective Film is Formed Through only Sputtering)

[0210] A disk D was produced in a manner similar to that described inExample 1.

[0211] On the disk D, a protective film predominantly containing carbonwas formed through sputtering under the conditions shown in Table 1. InExamples 14 through 16, the protective film was formed whilehigh-frequency bias (frequency: 13.56 MHz, power: 200 W) was applied tothe disk. In Comparative Example 1, the protective film was formedwithout application of bias. The thickness of the protective filmpredominantly containing carbon was 50 Å. Subsequently, a lubricationlayer was formed in a manner similar to that described in Example 1.

COMPARATIVE EXAMPLE 2

[0212] (A Protective Film is Formed Through Conventional CVD)

[0213] The procedure of Example 1 was repeated, except that theprotective film was not subjected to modification, to thereby produce amagnetic recording medium.

[0214] In each Example, before application of the lubricant, the surfaceof the magnetic recording medium was subjected to infrared spectroscopybefore and after formation of the protective film predominantlycontaining carbon, and the infrared spectrum of the protective film wasobtained. Subsequently, the intensity of the peak corresponding to acarbon-hydrogen bond was obtained. The infrared spectrum was measured ata point 20 mm along the radius of the disk. The results are shown inTable 1.

[0215] A fly stiction test was carried out in the following manner.

[0216] Firstly, a magnetic head (an MR head employed in a practicalmagnetic recording and reproducing apparatus) was placed on a position19.5 mm along the radius of the magnetic recording medium, and themedium was rotated at a rotation rate of 7,200 rpm at 40° C. and 80%humidity. Subsequently, the position of the head was moved to a position44 mm along the radius of the medium, and the medium was allowed tostand for 18 hours while being rotated. Subsequently, the position ofthe head was returned to the position 19.5 mm along the radius, rotationof the medium was stopped, and then the medium was allowed to stand forsix hours. Thereafter, the magnetic recording medium was subjected toone cycle of CSS (contact-start-stop) operation including (a cycle ofrising to 7,200 rpm for five seconds, operation at 7,200 rpm for onesecond, falling for five seconds, and parking for one second). Aftercompletion of the fly stiction test, deposition of the lubricant ontothe head was evaluated as follows. The head surface facing the disk wasobserved under an optical microscope (magnification: ×240), and the headhaving deposits on its surface was counted as “generation of deposits.”The results are shown in Tables 1, 2, and 3.

[0217] The extraction amount of melamine was measured in the followingmanner. The magnetic recording medium of each of the Examples and theComparative Examples was placed on a spindle in a commercially availablemagnetic recording and reproducing apparatus. Separately, a polyurethanepaste (2 g) was mixed with melamine (1 mass %), and the resultantmixture was applied onto a piece of aluminum foil (70 mm×25 mm) anddried. The thus-prepared piece, serving as an impurity gas generationsource, was placed in the apparatus together with the medium, andallowed to stand at 80° C. and 20% RH for 30 hours while the medium wasrotated at 3,000 rpm. Thereafter, the medium was removed from theapparatus, and was immersed for one hour in ethanol (30 ml) heated at80° C. The extracted melamine was quantitatively measured by means of aGC—MS apparatus (Automass, product of Nippon Denshi). The results areshown in Tables 1, 2, and 3.

[0218] The amount of nitrogen in the surface of the protective film wasmeasured by means of an ESCA apparatus (Sage100, product of Specs), andthe ratio of nitrogen to carbon was calculated on the basis of thefollowing formula. The results are shown in Tables 1, 2, and 3.

Ratio of nitrogen to carbon (%)=(N1s peak area)/(C1s peak area)×100

[0219] The apparatus and measurement conditions are as follows:

[0220] anode: aluminum;

[0221] spot size: 2-3 mm; and

[0222] area: obtained through a fitting method (C: Gaussian fitting, Nand O: Gaussian+Lorentz fitting).

[0223] The carbon protective film was analyzed through Ramanspectroscopy (light source: Ar laser, wavelength: 514.5 nm, output: 100mW, exposure time: 10 seconds, area: obtained through Gaussian fitting)by use of a Raman spectroscopic apparatus (product of Jobin-Yvon). Theresults are shown in Tables 1, 2, and 3. TABLE 1 Generation of depositson head Melamine Ratio Intensity [number of Protective Sputteringextraction of N to of peak head having film CVD protective protectivefilm amount C on correspond- deposits/ formation film formationformation Modification [μg/100 surface ing to Id/ number of processconditions conditions conditions cm²] [%] C—H bond Ig sample Ex. 1 AfterRF: 750 W None RF 120 W, 3 sec 1.26 17.6 0.014 1.37 0/10 formation ofBias mean voltage: N₂ gas: 100 sccm a protective −100 V Pressure: 4.2 Pafilm through Bias pulse width: CVD, the 500 ns film was Bias pulsesubjected to frequency: 150 kHz modification Bias positive by use of N₂voltage: 50 V gas Gas: C4H6/H2 = 44/143 sccm Pressure: 4.5 Pa Ex. 2After ″ ″ RF 120 W, 3 sec 0.23 ND 0.022 0.8 3/10 formation of O₂ gas:100 sccm (Not a protective Pressure: 4.3 Pa De- film through tected)CVD, the film was subjected to modification by use of O₂ gas Ex. 3 After″ ″ RF 120 W, 3 sec 0.19 ND 0.015 1.2 3/10 formation of Ar gas: 130 sccma protective Pressure: 4.7 Pa film through CVD, the film was subjectedto modification by use of Ar gas Ex. 4 After ″ DC 1500 W, 2.0 sec None0.48 27.3 ND 1.85 1/10 formation of Ar gas: 75 sccm a protective N₂ gas:25 sccm film through Pressure: 0.73 Pa CVD, another Rf bias: 200 Wprotective film was formed through sputtering by use of N₂ and Ar gasEx. 5 After ″ DC 1500 W, 2.0 sec None 0.53 28.6 ND 1.92 1/10 formationof Ar gas: 75 sccm a protective N2 gas: 25 sccm film through Pressure:0.73 Pa CVD, another Rf bias: 400 W protective film was formed throughsputtering by use of N₂ and Ar gas Ex. 6 After ″ DC 1500 W, 2.0 sec None0.41 23.1 ND 1.77 1/10 formation of Ar gas: 75 sccm a protective N₂ gas:25 sccm film through Pressure: 0.73 Pa CVD, another Bias mean voltage:protective −200 V film was Bias pulse width: formed 500 ns through Biaspulse sputtering frequency: 150 kHz by use of N₂ Bias positive and Argas voltage: 50 V Ex. 7 After ″ DC 1500 W, 2.0 sec None 0.48 26.5 ND1.84 1/10 formation of Ar gas: 75 sccm a protective N₂ gas: 25 sccm filmthrough Pressure: 0.73 Pa CVD, another Bias mean voltage: protective−300 V film was Bias pulse width: formed 500 ns through Bias pulsesputtering frequency: 150 kHz by use of N₂ Bias positive and Ar gasvoltage: 50 V

[0224] TABLE 2 Generation of deposits on head Melamine Ratio Intensity[number of Protective Sputtering extraction of N to of peak head havingfilm CVD protective protective film amount C on correspond- deposits/formation film formation formation Modification [μg/100 surface ing toId/ number of process conditions conditions conditions cm²] [%] C—H bondIg sample Ex. 8 A protective RF: 750 W None None 0.23 ND 0.028 1.02 3/10film was Bias mean voltage: a protective −250 V formed Bias pulse width:through CVD 500 ns with Bias pulse application frequency: 150 kHz ofbias Bias positive voltage: 50 V Gas: C4H6/H2 = 44/143 sccm Pressure:4.5 Pa Ex. 9 A protective RF: 750 W None None 0.27 ND 0.020 1.13 3/10film was Bias mean voltage: formed −300 V through CVD Bias pulse width:with 500 ns application Bias pulse of bias frequency: 150 kHz Biaspositive voltage: 50 V Gas: C4H6/H2 = 44/143 sccm Pressure: 4.5 Pa Ex.10 A protective RF: 750 W None None 0.29 ND 0.013 1.31 4/10 film wasBias mean voltage: formed −700 V through CVD Bias pulse width: with 500ns application Bias pulse of bias frequency: 150 kHz Bias positivevoltage: 50 V Gas: C4H6/H2 = 44/143 sccm Pressure: 4.5 Pa Ex. 11 Aprotective RF: 750 W None None 0.14 ND 0.057 0.52 6/10 film was Biasmean voltage: formed −50 V through CVD Bias pulse width: with 500 nsapplication Bias pulse of bias frequency: 150 kHz Bias positive voltage:50 V Gas: C4H6/H2 = 44/143 sccm Pressure: 4.5 Pa Ex. 12 A protective RF:750 W None None 0.17 ND 0.052 0.55 4/10 film was Bias RF: 50 W formedBias: 13.56 MHz through CVD Gas: C4H6/H2 = with 44/143 sccm applicationPressure: 4.5 Pa of bias Ex. 13 A protective RF: 750 W None None 0.20 ND0.031 0.93 4/10 film was Bias RF: 150 W formed Bias: 13.56 MHz throughCVD Gas: C4H6/H2 = with 44/143 sccm application Pressure: 4.5 Pa of bias

[0225] TABLE 3 Generation of deposits on head Melamine Ratio Intensity[number of Protective Sputtering extraction of N to of peak head havingfilm CVD protective protective film amount C on correspond- deposits/formation film formation formation Modification [μg/100 surface ing toId/ number of process conditions conditions conditions cm²] [%] C—H bondIg sample Ex. 14 A protective None DC 1500 W, 11 sec None 0.32 ND ND3.38 2/10 film was Ar gas: 85 sccm formed Pressure: 0.70 Pa through onlyRf bias: 200 W sputtering Ex. 15 A protective None DC 1500 W, 11 secNone 0.56 31.8 ND 2.33 1/10 film was Ar gas: 75 sccm formed N₂ gas: 25sccm through only Pressure: 0.73 Pa sputtering Rf bias: 200 W Ex. 16 Aprotective None DC 1500 W, 11 sec None 0.09 ND 0.013 1.86 6/10 film was5 vol % CH4 in Ar: formed 85 sccm through only Pressure: 0.70 Pasputtering Rf bias: 200 W Comp. A protective None DC 1500 W, 11 sec None0.05 ND 0.017 1.79 10/10 Ex. 1 film was 5 vol % CH4 in Ar: formed 85sccm through only Pressure: 0.70 Pa sputtering No bias Comp. Aprotective RF: 750 W None None 0.02 ND 0.042 0.74 10/10 Ex. 2 film wasBias mean voltage: formed −100 V through Bias pulse width: conventional500 ns CVD Bias pulse frequency: 150 kHz Bias positive voltage: 50 VGas: C4H6/H2 = 44/143 sccm Pressure: 4.5 Pa

[0226] Industrial Applicability

[0227] According to the inspection method of the present invention,without performance of a time-consuming test, generation of depositsonto a magnetic head can be easily inspected by comparing apredetermined threshold with the extraction amount of an inspection gascomponent and/or a compound component formed so as to contain theinspection gas component, the gas component and/or the compoundcomponent being extracted with an inspection solvent after a magneticrecording medium is allowed to stand in an atmosphere of the inspectiongas component. According to the inspection method, there can bedetermined conditions for the production of a magnetic recording medium,such that generation of deposits onto a magnetic head can be prevented.In addition, the inspection results can be reflected in the productionof the magnetic recording medium.

[0228] According to the magnetic recording medium of the presentinvention, the extraction amount of an inspection gas component and/or acompound component formed so as to contain the inspection gas componentis equal to or greater than a certain threshold, the gas componentand/or the compound component being extracted with an inspection solventafter the magnetic recording medium is allowed to stand in an atmosphereof the inspection gas component. Therefore, since the magnetic recordingmedium exhibits improved fly stiction characteristic, the medium can beused while the flying height is maintained at a low level, and used athigh recording density.

[0229] According to the production process of the present invention, theaforementioned magnetic recording medium can be easily produced, sincethe aforementioned inspection method is carried out.

[0230] According to the magnetic recording and reproducing apparatus ofthe present invention including the aforementioned magnetic recordingmedium, high recording density can be realized, since fly stictioncharacteristic is improved and the distance between the medium and amagnetic head can be reduced.

What is claimed is:
 1. A method for inspecting depositioncharacteristics of a deposit on the surface of a protective filmpredominantly containing carbon of a magnetic recording medium, whichmedium comprises a disk and the protective film formed on the disk, thedisk comprising a non-magnetic substrate, a non-magnetic undercoatlayer, and a magnetic layer, the layers being formed on the substrate,characterized in that the method comprises determining that theextraction amount of an inspection gas component and/or a compoundcomponent formed so as to contain the inspection gas component is equalto or greater than a predetermined threshold, the gas component and/orthe compound component being extracted with an inspection solvent afterthe magnetic recording medium is allowed to stand in an atmosphere ofthe inspection gas component.
 2. An inspection method according to claim1, wherein the inspection gas component is a gas generated in a magneticrecording and reproducing apparatus comprising a magnetic recordingmedium and a magnetic head for recording data onto the medium andreproducing the data therefrom.
 3. An inspection method according toclaim 1, wherein the inspection gas component is one or more selectedfrom among a siloxane-containing gas, an acrylic-acid-containing gas,vaporized melamine, a vaporized lubricant, a vaporized higher fattyacid, a vaporized phthalic acid ester, and vaporized dioctyl phthalate.4. An inspection method according to claim 1, wherein the inspection gascomponent is a gas component generated from a member employed inside themagnetic recording and reproducing apparatus.
 5. An inspection methodaccording to claim 1, wherein the inspection solvent is one or moreselected from among methanol, ethanol, isopropyl alcohol, and water. 6.An inspection method according to claim 1, wherein the threshold is 0.06[μg/100 cm²] when the extracted component is melamine.
 7. A magneticrecording medium comprising a non-magnetic substrate; a non-magneticundercoat layer and a magnetic layer, the layers being formed on thesubstrate; and a protective film predominantly containing carbon, thefilm being formed on the magnetic layer, characterized in that theextraction amount of an inspection gas component and/or a compoundcomponent formed so as to contain the inspection gas component is equalto or greater than a predetermined threshold, the gas component and/orthe compound component being extracted with an inspection solvent afterthe magnetic recording medium is allowed to stand in an atmosphere ofthe inspection gas component.
 8. A magnetic recording medium accordingto claim 7, wherein the threshold is 0.06 [μg/100 cm²] when theextracted component is melamine.
 9. A magnetic recording mediumaccording to claim 7, wherein a peak of the infrared spectrum of thesurface of the protective film predominantly containing carbon, the peakcorresponding to a carbon-hydrogen bond, has an intensity of 0.055 orless.
 10. A magnetic recording medium according to claim 7, wherein theratio of nitrogen to carbon in the protective film predominantlycontaining carbon is 5-40 at %.
 11. A magnetic recording mediumaccording to claim 7, wherein Id/Ig of the surface of the protectivefilm predominantly containing carbon is 3.5 or less.
 12. A process forproducing a magnetic recording medium, which process comprises forming aprotective film predominantly containing carbon on a disk comprising anon-magnetic substrate, a non-magnetic undercoat layer, and a magneticlayer, the layers being formed on the substrate, characterized in thatthe protective film is formed such that the extraction amount of aninspection gas component and/or a compound component formed so as tocontain the inspection gas component is equal to or greater than apredetermined threshold, the gas component and/or the compound componentbeing extracted with an inspection solvent after the magnetic recordingmedium is allowed to stand in an atmosphere of the inspection gascomponent.
 13. A production process for a magnetic recording mediumaccording to claim 12, wherein a formation process for the protectivefilm predominantly containing carbon comprises a sputtering process inwhich the protective film is formed while bias is applied to the disk.14. A production process for a magnetic recording medium according toclaim 12, wherein a formation process for the protective filmpredominantly containing carbon comprises a plasma CVD process in whicha reaction gas containing hydrocarbon is employed as a raw material. 15.A production process for a magnetic recording medium according to claim12, wherein a formation process for the protective film predominantlycontaining carbon comprises a formation step including a plasma CVDprocess in which a reaction gas containing hydrocarbon is employed as araw material, and a formation step including a sputtering process inwhich the protective film is formed while bias is applied to the disk.16. A magnetic recording and reproducing apparatus comprising a magneticrecording medium and a magnetic head for recording data onto the mediumand reproducing the data therefrom, characterized in that the magneticrecording medium is a magnetic recording medium as recited in any one ofclaims 7 through 11.